How to grow potatoes in bags

If you’re lucky enough to have space on your vegetable plot you can grow your potatoes in the ground. If you only have limited space read this potato growing guide to find out how to grow potatoes in containers.

Nothing beats that freshly dug, earthy taste of your own home grown potatoes! Growing your own potatoes isn’t as complicated as you might think, particularly if you grow them in potato bags. It’s the perfect method for growing spuds in small gardens, patios or even on balconies! Potatoes growing in containers are also at much less risk of pests and diseases. From our range you can buy seed potatoes for cropping throughout most of the year, including seed potatoes for Christmas which are becoming increasingly popular.

When to grow potatoes

Potatoes are normally planted in March for harvesting throughout summer and autumn. They can also be planted in August/September for Christmas new potatoes (these are also known as Second Cropping Potatoes). Use the table below as a general guide on when to plant potatoes.

‘Chitting’ Potatoes

Seed potatoes, particularly earlies and second earlies benefit from 'chitting' which is the process of growing shoots on potato tubers prior to planting. The benefit is that this will produce faster growth and heavier crops.

You can start them off as soon as you receive them. Remove the seed potatoes from their packaging and lay them out in a cool, bright, frost free position. The tried and tested method is to set them out in egg boxes or seed trays. You will notice that the immature shoots are all at one end (called the rose end). Place the potatoes with this end facing upwards. By the time that you are ready to plant them, they will have produced shoots up to 25mm (1") in length.

There is one exception - second cropping potatoes do not require chitting and can be planted straight away.

Cutting Seed Potatoes

Seed potatoes are normally about the size of a chicken’s egg, but will often vary in size. Don’t be concerned if you receive different sized seed potatoes - they will all grow equally well.

In fact, during the 2nd World War it was common practice to cut larger seed potatoes in half or even smaller divisions to make the seed potatoes go further. The cuts should be left to dry out for 3 or 4 days before planting in the usual way. Provided that each piece has an eye or two for the new growth to develop, these tuber divisions will still crop well. Nowadays, seed potatoes are cheap and widely available so there is generally no need to do this unless you receive particularly large seed potatoes with lots of eyes.

How to plant potatoes in bags

Growing potatoes in planters is the perfect solution if you want to grow your own potatoes but have limited space. We offer some fantastic potato planter collections, which come ready to plant with potato growing bags and potato tubers, offering great value for money.

In the past, growing potatoes in bags has always involved 'earthing up' potatoes as they grow. But recent trials at Thompson and Morgan have shown that this isn't necessary, so planting potatoes on your patio has just got even easier.

To plant up potato grow bags in two easy steps:

Simply fill an 8 litre potato bag with good quality multipurpose compost to around 2.5cm (1") below the rim.

Carefully plunge a single chitted potato tuber into the compost with the shoots pointing upwards, to a depth of 12cm (5") from the soil surface. Gently cover the tubers with compost.

Now all you need to do is water them, place the potato bag in a bright, frost free position and wait for them to grow.

Feed potato plants every other week with potato fertiliser and water the bags when the compost begins to dry out.

Harvesting potatoes

Harvest times will vary depending on the growing season and the size of tuber you want. However the table at the top of the page provides a rough guide for each crop type.

Start to harvest first earlies as 'new potatoes' when the plants begin to flower, approximately 10 weeks from planting. It’s worth having a gentle dig below the surface to check the potato sizes - if they’re too small simply leave them for another week or so, otherwise lift them and enjoy!

Maincrop varieties are usually left for at least two weeks after the leaves and haulms (stems) have withered, to allow the skins to set. Cut down the stems with secateurs to just above soil level as the leaves wither and yellow, or if they show signs of blight.

Second cropping tubers are often called Christmas potatoes. These winter potatoes can be harvested as required from November, or left in the soil until Christmas. Cut down the foliage as the leaves wither and yellow, and protect them from frost by covering the potato growing bags with a thick layer of straw or moving them into the shed or greenhouse.

Storing Potatoes

After harvesting, set the tubers out in a dry, well ventilated position for a few hours to dry and cure the skin. Once dry store them in paper or hessian potato sacks in a dark, cool but frost free place. Avoid storing in polythene bags as potatoes will 'sweat' and rot.

Potato problems

Late Blight

Symptoms: Late blight is particularly prevalent during warm humid weather and wet periods in late summer. Dark brown blotches appear on the leaves, particularly towards the leaf tips and edges. White fungal spores develop around these lesions on the undersides of the leaves, and further lesions develop on the stems. Leaves and stems rapidly blacken and rot causing plant collapse. The spores are released on the wind and quickly spread to infect neighbouring plants. Spores may also be washed down into the soil where they can infect potato tubers causing a red-brown rot directly beneath the skin which slowly spreads towards the centre of the tuber.

Remedy: Spray potato crops with a protective fungicide even before signs of blight become apparent. Begin spraying this potato blight treatment from about June, particularly when periods of wet weather are forecast and spray again after a few weeks to protect any new growth. If plants become infected they should be removed and destroyed. Where potato crops have already developed tubers then these can be saved by cutting away the foliage and stems. Leave the soil undisturbed for 2/3 weeks to kill off any lingering spores so that they don’t infect the crop when it is lifted.

Slugs

Symptoms: Slugs cause damage to both the foliage and to the developing potato tubers. Damage is fairly obvious as the culprits are easily identified by the silvery slime trails that are left around the plant foliage and on the soil surface.

Remedy: There are a multitude of ways to kill slugs and snails including homemade remedies such as beer traps. The most common method is to use slug pellets or for the more organically minded gardener you can try nematodes or copper tape.

Potato Scab

Symptoms: Common Scab leaves corky lesions on the skins of potatoes and limits their storage potential. Whilst this disease does not affect the taste and can easily be peeled off, it does make potatoes less visually appealing. It is caused by a bacteria that is often present in manures and is exacerbated in limy and sandy soils, and under dry conditions.

Remedy: Common Scab on potatoes is best controlled by improving poor soil conditions with the addition of organic matter and by keeping potato crops well watered throughout the growing season. Use any infected tubers first and do not store them.

Eelworm

Symptoms: There are two types of Potato cyst eelworms - the golden eelworm and the white eelworm. Plant growth is checked and potato yields are reduced. The foliage of severely infected plants turns yellow and dies back early prematurely, often in conspicuous patches where the soil in infested with eelworms. The presence of Eelworm cam be confirmed by inspecting the roots of damaged plants, where minute pinhead sized cysts can be seen. They will be white, yellow or brown in colour.

Remedy: There are no effective remedies to serious infestations other than to refrain from growing potatoes in infected soils for at least 6 years. Practice good crop rotation to prevent infestations building up in the soil. Eelworm resistant varieties are available but are not immune from attack.

Blackleg

Symptoms: Potato Blackleg is spread through contact and is particularly prevalent in cool, wet and poorly drained soils. This bacterial disease causes blackening of the stems, close to soil level as the stems begin to rot. Ultimately stems will collapse. Yellowing and browning of the leaves may also occur. Affected tubers display grey or brown slimy rot inside or may rot away completely.

Remedy: Blackleg generally infects individual plants rather than entire crops and does not spread between plants or persist in the soil. Remove and destroy any infected plants, improve soil drainage and plant blackleg resistant potato varieties.

Growing potatoes in the ground

If you're lucky enough to have a bit more space why not try growing potatoes in the ground? Click here to find out how to grow potatoes in the ground.

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Written by: Sue Sanderson

Plants and gardens have always been a big part of my life. I can remember helping my Dad to prick out seedlings, even before I could see over the top of the potting bench. As an adult, I trained at Writtle College where I received my degree, BSc. (Hons) Horticulture. After working in a specialist plantsman's nursery, and later, as a consulting arboriculturalist, I joined Thompson & Morgan in 2008. Initially looking after the grounds and coordinating the plant trials, I now support the web team offering horticultural advice online.